As the above-mentioned type apparatus, a substrate transfer apparatus for an electronic component mounting machine shown in FIG. 5, for example, has been conventionally provided. FIG. 5 is a perspective view of an electronic component mounting machine 1 including a conventional substrate transfer apparatus; FIGS. 6A-6D are sequential views showing a substrate transfer process in the conventional substrate transfer apparatus; and FIGS. 7A-7D are sequential views showing a process of simultaneous transfer of substrates in the conventional substrate transfer apparatus. Among the above-listed figures, FIGS. 6A, 6C, 6D, 7A, 7C, and 7D are views of the substrate transfer apparatus seen from above the apparatus, while FIGS. 6B and 7B are views of the substrate transfer apparatus shown in FIGS. 6A and 7A, respectively, seen from the side of the apparatus.
In FIGS. 5, 6A-6D and 7A-7D, the reference numeral 2 denotes a mounted substrate; 3 an unmounted substrate; 4a, 4b and 4c entrance substrate detecting sensors; 5a, 5b and 5c substrate-arrival detecting sensors; and 10a, 10b and 10c transfer belts. This substrate transfer apparatus has a mounting-waiting process 7, a mounting process 8 and a substrate discharge-waiting process 9. Arrows in FIGS. 5-7D represent a substrate transfer direction. According to such a conventional substrate transfer apparatus, by rotating the transfer belts 10a, 10b, and 10c shown in FIG. 6B, the unmounted substrate 3 can be transferred from the mounting-waiting process 7 to the mounting process 8, and the mounted substrate 2 can be transferred from the mounting process 8 to the substrate discharge-waiting process 9 sequentially.
The above transfer process is described more specifically. In the processes shown in FIGS. 6A and 6B, the transfer belt 10b is first rotated. After the entrance substrate detecting sensor 4c detected the mounted substrate 2, the transfer belt 10c is rotated to transfer the mounted substrate 2 into the substrate discharge-waiting process 9. The fact that the mounted substrate 2 has completely entered the substrate discharge-waiting process 9 can be determined by detecting that the entrance substrate detecting sensor 4c of the substrate discharge-waiting process 9 was placed on a substrate-detected state after the rotation of the transfer belt and thereafter the state of the sensor 4c turned into an undetected state.
By keeping the transfer belts 10b and 10c rotating and further rotating the transfer belt 10a, the unmounted substrate 3 is transferred from the mounting-waiting process 7 to the mounting process 8. FIG. 6C shows a state immediately after the rotation of the transfer belt 10a started.
After the state shown in FIG. 6C, upon detection of the mounted substrate 2 by the substrate-arrival detecting sensor 5c of the substrate discharge-waiting process 9, the rotation of the transfer belt 10c is stopped, thereby finishing the transfer of the mounted substrate 2 from the mounting process 8 to the substrate discharge-waiting process 9. Moreover, when the substrate-arrival detecting sensor 5b of the mounting process 8 detected the unmounted substrate 3, the rotation of the transfer belt 10b is stopped, thereby finishing the transfer of the unmounted substrate 3 from the mounting-waiting process 7 to the mounting process 8. FIG. 6D shows this state.
However, in the above-described transfer process, waiting time is generated from determination that the mounted substrate 2 has completely entered the substrate discharge-waiting process 9 to the start of the transfer of the unmounted substrate 3. In order to reduce the time required for the transfer operation, there is a method in which that waiting time is eliminated and the transfer of the mounted substrate 2 and that of the unmounted substrate 3 simultaneously start. For example, a method for simultaneously transferring a plurality of substrates is effective.
The aforementioned simultaneous transfer method is described more specifically, referring to a substrate transfer apparatus for transferring two substrates simultaneously as an example. In the process shown in FIGS. 7A and 7B, the transfer belts 10a, 10b, and 10c are activated to rotate simultaneously. Thus, it is possible to simultaneously start the transfer of the mounted substrate 2 and the transfer of the unmounted substrate 3. FIG. 7C shows a state immediately after the transfer start of the mounted substrate 2 and unmounted substrate 3. Then, when the substrate-arrival detecting sensor 5c in the substrate discharge-waiting process 9 has detected the mounted substrate 2, the rotation of the transfer belt 10c is stopped. Moreover, when the substrate-arrival detecting sensor 5b in the mounting process 8 has detected the unmounted substrate 3, the rotation of the transfer belts 10a and 10b is halted. As a result, the transfer of the mounted substrate 2 and unmounted substrate 3 is finished. This state is shown in FIG. 7D.
However, when the simultaneous transfer method is performed by using the conventional substrate transfer apparatus described above, a trouble may occur during the transfer of the preceding substrate, for example, the mounted substrate 2 may be got stuck during the transfer. In this case, there is a problem that the following substrate, such as the unmounted substrate 3, catches up with the preceding substrate having the trouble and, if the following substrate eliminates the trouble of the preceding substrate by the impact when the following substrate catches the preceding substrate, a plurality of substrates are transferred to the downstream process continuously.
FIGS. 8A-8D are diagrams showing a process of occurrence of the problem during the simultaneous transfer of a plurality of substrates in the conventional substrate transfer apparatus. In FIGS. 8A-8D, the reference numeral 2 denotes a mounted substrate; 3 an unmounted substrate; 4a, 4b and 4c entrance substrate detecting sensors; 5a, 5b and 5c substrate-arrival detecting sensors; and 10a, 10b and 10c transfer belts. As is the case with FIGS. 5-7D, the reference numeral 7 denotes the mounting-waiting process; 8 the mounting process; and 9 the substrate discharge-waiting process. The arrow in FIGS. 8A-8D represents the substrate transfer direction.
The aforementioned problem is described more specifically, referring to simultaneous transfer of two substrates as an example. In the process shown in FIGS. 8A and 8B, the transfer of the mounted substrate 2 and the transfer of the unmounted substrate 3 are started simultaneously by starting to rotate the transfer belts 10a, 10b, and 10c simultaneously. FIG. 8C shows a state in which the preceding mounted substrate 2 became stuck after the start of the rotation of the transfer belts 10a, 10b, and 10c and the following unmounted substrate 3 caught up with the mounted substrate 2. If the mounted substrate 2 got out of the stuck state by the impact when the unmounted substrate 3 caught up with the mounted substrate 2, for example, the mounted substrate 2 and the unmounted substrate 3 are continuously transferred into the substrate discharge-waiting process 9 although the unmounted substrate 3 is to be stopped at the position of the substrate-arrival detecting sensor 5b in the mounting process 8. This is because the transfer belts 10b and 10c are being rotated. FIG. 8D shows this state.
In a case where the substrate transfer apparatus comes into such a state, when a substrate-request signal was output from equipment connected in the downstream process of the electronic component mounting machine 1 and thus the rotation of the transfer belt 10c was started so as to discharge the mounted substrate 2c, the unmounted substrate 3 was also discharged to the equipment connected in the downstream process. As a result, there is a problem that a defective substrate is generated in which components to be mounted have not been mounted during the process in the electronic component mounting machine 1.
The present invention was made considering the aforementioned two problems. It is an object of the present invention to provide a substrate transfer apparatus for a component mounting machine, that includes detection means for detecting continuous transfer of a plurality of substrates, thereby reducing transfer time, preventing occurrence of a defective substrate in advance, and improving the quality of produced substrates.